1) Field of the Invention
The present invention is directed to a system where a flight controller that controls aircraft landings and take-offs on a runway is able to observe the position and severity of wind conditions in close proximity to the aircraft runway.
2) Description of the Prior Art
Microbursts, which are also known as wind shear, have always been a serious hazard to aviation. The microburst is defined as a powerful downward blast of air usually associated with a thunderstorm or rain, followed by a violent horizontal burst of air in all directions (hence wind shear). Microbursts are relatively small such as two and a half miles in diameter or less, short lived, with ninety percent of the microburst reaching maximum velocity in ten minutes. A region of a superheated air some distance above the ground is initially penetrated by rain. The rain evaporates at a high rate to quickly reduce the air temperature and thereby increase the density of the superheated air. The now heavy air proceeds to move downwardly at an accelerating rate until it reaches ground level where it must now spread out horizontally. The short term nature of the microburst is explained since the rapid air fall causes a partial vacuum and thus as the air drops to the ground and is heated, it returns to reduce that partial vacuum. As additional rain penetrates the region, equilibrium results and the microburst terminates. Air has been found to gust down vertically as much as 4,000 feet per minute from distances of 2,000 feet from the ground. The basic shape of the microburst, if it could be seen, would be that of an inverted mushroom.
An aircraft flying through a microburst first encounters a head wind providing good lift. This head wind may be of up to fifty miles an hour. Then the aircraft, in a very short space of time and distance, encounters the opposite wind which now becomes a tail wind again at 50 miles an hour in the opposite direction. Thus the aircraft has now experienced a one hundred miles per hour air speed change over a distance as short as one mile. If an aircraft is flying flaps down and near landing speed and encounters a tail wind, the pilot experiences a sudden loss of air speed. If adjustments can not be made quickly enough, or if the plane is so heavily loaded or draggy that it can not make rapid accommodating changes, the aircraft may crash.
Explained a little differently, an aircraft during takeoff and landing is typically purposely operated near stall speed and the acceleration capabilities of large aircraft are inadequate to cope with large air speed variations. The first symptom of the microburst is a relatively rapid increase in the head wind. This increases the airflow across the wings and if nothing else is changed would induce the aircraft to rise above the desired flight path. The typical pilot would choose to throttle back (as the pilot is trained to do) so as to reduce air speed to a target air speed. Almost immediately a down draft occurs and the head wind disappears and a strong tail wind becomes prevalent. Because the pilot is now in a powered down mode, increased air speed to counteract the tail wind is now required. However, the aircraft does not have the acceleration capabilities to cope with this rapid wind variation and aircraft stalling and subsequent crash is quite frequently a common occurrence.
It is to be remembered that the only time the microburst becomes a really serious hazard is when it appears in close relation to an airport runway to thereby cause aircraft to rapidly change in altitude in areas where any significant change in altitude is disastrous. The aircraft in relation to the runway is being operated at a very low altitude.
Once a microburst is detected, the pilot can be warned and could maneuver the aircraft either around the microburst or if knowing what is going to occur, the pilot could possibly maneuver the aircraft safely through the microburst. One way in which this could occur would be by the pilot not powering down when first encountering the head wind. Preferably, however, since microbursts are known to have exceedingly short life time (ten to fifteen minutes), a microburst which is detected directly adjacent to an aircraft runway will result in terminating of aircraft operations on that runway for that period of time.
Another undesirable wind condition is the wake created when an aircraft takes off. If a following aircraft encounters a wake, an exceedingly dangerous condition will occur. To avoid such a problem, flight controllers provide ample time between aircraft take-offs. However, if a flight controller could actually observe when this wake has dissipated, many more aircraft could take off in a given length of time eliminating the excess time that is now allowed, thereby alleviating of the traffic that is so common within many airports.